Recent evidence demonstrates that the functional impairment or atrophy of pelvic muscles, such as levator ani, urethral supports and urethral sphincter, are responsible for stress urinary incontinence (SUI) in women. SUI is a common condition with significant morbidity, and treatment options include pelvic floor exercises, pharmacological treatment, and surgery. Currently, surgical management is the main treatment of genuine SUI and offers the highest cure rates. However, they are invasive and associated with complications, both intra- and post-operatively. There is, therefore, a constant search for a better approach to treat SUI. Cell-based therapies with adult stem cells of muscle origin (muscle-derived stem cells, MDSC) hold promise for tissue repair with the ultimate goal to regenerate and restore normal function of the pelvic support to the bladder, urethrovesical junction, and urethra. In recent years, adult stem cell implantation has been shown to regenerate myofibers in atrophic or injured skeletal muscle. Regeneration of smooth muscle has also been demonstrated. Adult stem cell implantation for the repair of defective tissues responsible for SUI is a novel and promising option for a therapy of this condition. Our overall goal of this study is to investigate, in a rat model, whether the implantation of autologous muscle-derived stem cells into the atrophic levator ani, with or without concurrent implantation into the striated urogenital sphincter or urethral smooth muscles, can reverse the atrophy and subsequently improve or cure SUI. The long-term objective is to eventually devise a clinical trial for the use of autologous stem cells in women for the correction of SUI. This study involves two aims. The first aim involves the in vitro isolation, purification, and characterization of rat muscle derived stem cells. The outcomes will include the determination of myotube formation, smooth muscle cell differentiation, and myofibroblast formation. These tests will determine whether the ongoing cell culture is still active in generating skeletal and smooth muscles in the absence of myofibroblasts. The second aim is to determine the effects of implanting autologous stem cells into the atrophic levator ani of female rats, with or without concurrent implantation into the striated urogenital sphincter or urethral smooth muscles. The outcomes include urodynamic measurements, stress test, skeletal muscle weight, fate of the implanted stem cells, and cell lineage determination.